Reply #10: Most apt analogies are 1980 and 1992

[featherman]

In both cases an incumbent with sinking approval ratings was facing a challenger. In these two elections swing voters had mostly made up their minds about the incumbent and were kind of checking out the challenger to see if he was up to the job. More broke to the challenger than the incumbent once that was confirmed. This tipping point came fairly early for Clinton and quite late for Reagan. It is not yet reached for Kerry but may be in sight.
1988 and 2000 were more like "open seat" elections with new guys on each side. Unfortunately, "comfort level" seemed to be the determining factor in electing Poppa Bush over Dukakis and making 2000 close enough for W. to steal.